Weird Science thinks seven sexes is enough for anybody

But isn't sure whether a three-headed shark might not be better.

Dance of the seven veils sexes.Tetrahymena is a single-celled organism that looks a bit like a microscopic ball of fuzz, since it's covered with cilia. Despite its unshaven appearance, the cells can mate, although they'll also simply divide asexually if there's nobody around. (A Weird Science Fact: Tetrahymena has a set of chromosomes they carry around that are reserved for having sex. The rest of the time, a completely different set helps run the cell.) Of course, that creates a problem: as soon as they divide, there is somebody around, but mating with a cell that's genetically identical is a bit of a waste of time. So, the organism uses something akin to sexes to avoid this. If it divides, the two cells that result will be the same sex, and can't mate.

All very sensible, until you get to one tiny detail: for no obvious reason, Tetrahymena have decided they need seven sexes. The new paper figures out how that actually works. In the chromosomes used for mating, they have a set of seven inactive half-genes, located next to a different half gene that will ensure that the protein made from it ends up on the cell's surface. When mating occurs, one of the set of seven is selected at random, linked up to the other half, and converted into a functional gene. When the gene product is on the cell's surface, that cell will not be able to mate with any other cell that has the same arrangement.

Now we'll need an extra set of lasers. If you were to happen across this two-headed shark foetus, what would your first thought be? If you were a biologist, it would apparently be "I wonder if this is a case of the fusion of twin shark embryos, or if this is really a single embryo with two heads?" Fortunately, said biologists now have an answer: one shark, two heads.

A public safety effort that is decreasing public safety. After a few horror stories of botched medical care that were the product over overworked, sleep-deprived residents, a number of programs cut back on how many hours these residents were allowed to work each week. And, as a result, they're apparently making more mistakes than they did while being on-duty for 72-hour shifts. A survey of residents shows that, while they're working fewer hours, they're being expected to get the same amount done—just faster. Plus, since they go off work sooner, they have to hand all their patients off to new doctors, which can also increase the problems with care. And, in the ultimate irony, for whatever reason, the residents don't report getting any more sleep than they used to.

Cell phone conversations aren't any more distracting—but they are more annoying. If you've ever found yourself getting irate about hearing half of a conversation that's spoken into a cell phone, you're hardly alone. But is that any worse than being subjected to both sides of a conversation? Depends on how you define worse. Subjects were asked to complete a task while being subjected to one or both sides of a scripted conversation. When it came to their task scores, both types of conversations were equally distracting. But there was some evidence that the participants paid more attention to the cell-phone-style one: they remembered more words from the conversation than they did from the two-way chat. And, if there were any doubts, they consistently rated the one-way conversation as being more annoying.

Taking the sting out of the stingray lifestyle. Stingrays are nocturnal feeders that lead a solitary lifestyle. Unless, that is, you invite a small horde of tourists to start feeding them. In that case, the animals seem to be perfectly willing to start staying awake all day, and hanging out at a population density that's just not seen anywhere else. They also become homebodies, staying close to the feeding site for extended periods of time. The authors of the analysis worry that all the changes will have "downstream fitness costs" that might need to be paid if, say, the tourists decide they'd rather be feeding some other species.

Dance of the seven veils sexes. Tetrahymena is a single-celled organism that looks a bit like a microscopic ball of fuzz, since it's covered with cilia. Despite its unshaven appearance, the cells can mate, although they'll also simply divide asexually if there's nobody around. (A Weird Science Fact: Tetrahymena has a set of chromosomes they carry around that are reserved for having sex. The rest of the time, a completely different set help run the cell.) Of course, that creates a problem: as soon as they divide, there is somebody around, but mating with a cell that's genetically identical is a bit of a waste of time. So, the organism uses something akin to sexes to avoid this. If it divides, the two cells that result will be the same sex, and can't mate.

Do State/Gov't agencies count as a "business"? Because that's certainly not true where I work. We lose people, less work is accomplished until the people can be replaced (which usually takes 6-9 months)

So, the next medical statistic I'd like to see. The number of patients per doctor, and doctors per capita from the era of house-calls vs. The same now.

The cold sterilization of our med-tech has been said to have a distinct effect on the breakdown of the patient-doctor relationship. I wonder if simply having less time per person may be amplifying this effect.

Thanks for a nice summary of the paper and links to other interesting cilate work. One of the interesting points of this work is the apparent necessary coupling of a poor environment (starvation) and sex. To my mind, this suggests that much of the randomness of the gender draw is related to maintaining as much variation as possible, that is to reduce linkage to genes that in one circumstance will be useful but in another not. I don’t follow the genetic logic at this reading to understand whether this actually results from the mechanisms found but it seems to be a possibility.

Nobody should be surprised that medical residents error rates aren't improving. Medical educators have resisted the changes for years. Hospitals don't want to lose the cheap labor force. So to keep costs down, they just expect the residents to do more with less . . . as in hours.

Which pretty much blows the whole preposition that residents actually need to work longer hours to get greater opportunities to see more kinds of cases, and reinforces that the accrediting organizations are going to have to get involved to force change beyond simply a matter of hours worked in order to improve patient safety . . . as in JCAHO.

In the meantime, don't let yourself get admitted to a teaching hospital in July. That's when the death rate from resident errors is the highest.

As for cell phone conversation annoyance . . . oh I so totally agree. A few weeks ago, I had to listen to another woman give a play by play description of her bowel movement to some friend over her cell phone . . . while we were in the ladies room and she was doing her business.

There needs to be a 'netiquette for cell phones. Seriously . . . it was gross.

Do State/Gov't agencies count as a "business"? Because that's certainly not true where I work. We lose people, less work is accomplished until the people can be replaced (which usually takes 6-9 months)

Your state/gov't agency might be somewhat unique.

My partner used to work for a state road authority, and dropped to 3 days a week due to a long term illness. She ended up getting sicker and eventually throwing in the whole job because she was still expected to do 5 days work in 3 days time.

I have to admit to being disappointed by this coverage to the Tetrahymena story. Seven sexes is certainly strange and attention grabbing (I led with it in my coverage of the story, too), but it seems remiss not to mention that it's not actually that unusual. There are fungi with tens, hundreds or even thousands of different sexes. The "sexes" in these cases are actually "mating types", which are much more like self/non-self recognition than our conception of "sex". Cells with different mating types are essentially the same, they're just sexually incompatible. To use an analogy, think of each mating type as a color; only cells of different colors can mate.

The really interesting part of the story (and the point of the paper) is how these mating types get determined. I've already described that in my blog post, so I won't repeat the details here. It's a really neat system, though, that has nothing to do with the XY/ZW sex determination systems. It's actually much more similar to how our immune system generates antibodies. The DNA editing mechanism must be really precise; since Tetrahymena is a model organism, we can hopefully use it to learn about how that works.

By the way, we have a whole bunch of cells that we "carry around that are reserved for having sex" -- sperm and eggs. The rest of the time, we use a completely different set (the rest of the body). I actually think it's pretty cool that Tetrahymena have come up with their own germline/somatic division system, despite being unicellular.